1. Field of the Invention
The present invention relates to heat-insulating structures for combustion equipment, which are to be used in thermal equipment such as boilers and incinerators. More specifically, the invention relates to a heat-insulating structure for combustion equipment of such a type that the burner element of combustion equipment is installed so as to be insertedly disposed at an installation opening of thermal equipment such as a boiler.
2. Description of the Prior Art
Combustion equipment, particularly those used in thermal equipment such as boilers and incinerators, are installed to the installation opening of the thermal equipment via a thermal insulator (or sealant) so as to effectively utilize heat generated by combustion without escaping it out of the system, and to prevent combustion gas from leaking outside the thermal equipment through the portion where the combustion equipment is installed.
prior art example of such installation structure is now described with reference to FIG. 5. FIG. 5 illustrates a boiler, as a typical example of thermal equipment A, in which a multiplicity of vertical water tubes X, X, . . . are arranged in a combustion chamber in such a relatively dense state that the combustion chamber has almost no combustion space.
Referring to FIG. 5, the vertical water tubes X located on both sides are arranged in a single line on either side, with adjoining vertical water tubes X connected to each other by connecting members Y, Y, . . . , so that a pair of water tube walls generally parallel to each other are formed. This pair of water tube walls define a passage Z through which combustion flame or combustion gas from combustion equipment B is distributed. Within the passage Z, a multiplicity of vertical water tubes X, X, . . . are insertedly provided over the generally entire range of the passage Z with enough spacings to allow the combustion flame or combustion gas to be distributed.
The combustion equipment B in FIG. 5 is intended to explain the premix type gas burner as an example. The combustion equipment B comprises a premixed gas supply passage 10 defined by a wind box 11, and a burner element 20 fixed at a specified position of the supply passage 10. The burner element 20 is formed into specified shape and size by a support frame 30 and installed to the thermal equipment A so as to be insertedly disposed at an installation opening 1 of the thermal equipment A. In this installation structure, a thermal insulator 40 is installed outside the support frame 30, thereby thermally protecting the support frame 30 and moreover thermally insulating and sealing the thermal equipment A and combustion equipment B from each other.
In the above-described conventional structure, the support frame 30 needs to have a retainer 31 bent toward the surface of the burner element 20 around the support frame 30 in order to retain the burner element 20 with stability and security. However, the retainer 31 serves as a heat-receiving surface that is subject to radiated heat if the combustion flame during combustion, thus easy to overheat. This requires the retainer 31 to be covered with the thermal insulator 40 for its protection's sake.
Also, in such conventional structure as described above, since the thermal insulator 40 between the thermal equipment A and the combustion equipment B is easily damaged during installation and removal of the combustion equipment B, the thermal insulator 40 is provided in a double structure for its secure protection. More specifically, a first thermal insulator 41 is disposed outside the support frame 30, and a holder member 43 for holding the first thermal insulator 41 and a second thermal insulator 42 for protecting the holder member 43 are further provided. However, even in this structure, the first and second thermal insulators 41, 42 need to be arranged so as to cover the surface of the burner element, 20, for protection of the retainer 31.
In the above-described prior art, since the flame by the combustion equipment B is formed at a position close to the surface of the burner element 20, the thermal insulator 40 is exposed directly to the flame. As a result, there would arise a problem that the thermal insulator 40 will wear early and may be stripped off. Also, since the thermal insulator 40 needs to be arranged so as to cover the surface of the burner element 20, high level of skills would be required to install the thermal insulator 40 as another problem.